The present invention relates to an optical system for crystallization tool, more particularly, to an optical system for crystallization tool for crystallizing an amorphous silicon thin film by using an excimer laser as an exposure light source through a fine-stripped pattern.
The conventional optical system for crystallization tool using the excimer laser as a light source, so as to crystallize amorphous silicon thin film has been restrictively used at the small area LCD of high density, not at the large area LCD, because the grain size of the crystallized silicon thin film was small and irregular. By using the conventional simple optical system, a large pattern of the silicon thin film of which size was 1 mmxc3x9750 mm was exposed to the light to crystallize the silicon. In this case, crystallization was depending on a crystallization seed existed in any local area within a silicon layer that is temporarily melted, because of its large pattern. Therefore, there is a problem that the grain size of the crystallized silicon thin film is small and irregular.
Therefore, the present invention is made in order to solve the problem described above.
An object of the present invention is to provide an optical system for crystallization tool enabling fabrication of a large area LCD, in which the fine stripped pattern having 2 xcexcm to 10 mm size is projected and exposed to the light by a projection optical system, and scanned gradually to grow the crystals, so that the grain size can be large and uniform.
The above object and other objects can be accomplished by an optical system for crystallization tool producing an crystallized silicon thin film by using an excimer laser as an exposure light source to crystallize an amorphous silicon thin film through a fine stripped pattern, comprising 1st to 10th lenses sequentially arranged along an optical axis from the excimer laser, the 1st lens having both side made convex; the 2nd lens having one side made convex toward the light source and the other side concave; the 3rd lens having one side made convex toward the light source and the other side concave; the 4th lens having both side concave; the 5th lens having both side made convex; the 6th lens having one side concave toward the light source and the other side made convex; the 7th lens having one side made convex toward the light source and the other side concave; the 8th lens having both side made convex; the 9th lens having one side made convex toward the light source and the other side concave; and the 10th lens having both side made convex.